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Old 07-10-2012, 07:06 AM
Emmanuel Noobadmin
 
Default Best way to duplicate a live Centos 5 server?

On 7/10/12, John R Pierce <pierce@hogranch.com> wrote:
> dump should not be used on mounted file systems, except / in single user.

Aha, thanks for the warning!
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Old 07-10-2012, 07:15 AM
John R Pierce
 
Default Best way to duplicate a live Centos 5 server?

On 07/10/12 12:06 AM, Emmanuel Noobadmin wrote:
> On 7/10/12, John R Pierce <pierce@hogranch.com> wrote:
>> dump should not be used on mounted file systems, except / in single user.
> Aha, thanks for the warning!
>

IF you're using LVM, you can take a file system snapshot, and dump the
snapshot, however, as this is a point-in-time replica of the file system.



--
john r pierce N 37, W 122
santa cruz ca mid-left coast

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Old 07-10-2012, 11:45 AM
Emmanuel Noobadmin
 
Default Best way to duplicate a live Centos 5 server?

On 7/10/12, John R Pierce <pierce@hogranch.com> wrote:
> IF you're using LVM, you can take a file system snapshot, and dump the
> snapshot, however, as this is a point-in-time replica of the file system.

Unfortunately I wasn't.

It does seem that essentially all the better methods that minimize
downtime require the system to be prepped when first installed, be it
LVM/MD/DRBD.

So going ahead, I'm basically making it a point to use MD mirror on
all new installs, including VMs that are not running RAID 1 virtually
as the physical storage is already RAIDed.

The assumption is that I should be able to just add an iSCSI target as
a member of the degraded RAID mirror, wait for it to sync, then
shutdown and start the new server within minutes as opposed to waiting
a couple of hours for rsync or any other forms of imaging/dump to
backup the current state.

The added benefit of this approach, it would seem is that I could use
that same approach to do backup of the entire fs.
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Old 07-10-2012, 05:26 PM
Les Mikesell
 
Default Best way to duplicate a live Centos 5 server?

On Tue, Jul 10, 2012 at 1:36 AM, Emmanuel Noobadmin
<centos.admin@gmail.com> wrote:
> On 7/9/12, Les Mikesell <lesmikesell@gmail.com> wrote:
>> One thing that helps is to break it up into separate runs, at least
>> per-filesystem and perhaps some of the larger subdirectories.
>> Depending on the circumstances, you might be able to do an initial run
>> ahead of time when speed doesn't matter so much, then just before the
>> cutover shut down the services that will be changing files and
>> databases and do a final rsync which will go much faster.
>
> I did try this but the time taken is pretty similar in the main delay
> is the part where rsync goes through all the files and spend a few
> hours trying to figure out what needs to be the updated on the second
> run after I shutdown the services. In hindsight, I might had been able
> to speed up things up considerably if I had generated a file list
> based on last modified time and passed it to rsync via the
> exclude/include parameters.

Hours? This should happen in the time it takes to transfer a
directory listing and read through it unless you used --ignore-times
in the arguments. If you have many millions of files or not enough
RAM to hold the list I suppose it could take hours.

>> Also, have you looked at clonezilla and ReaR?
>
> Yes, but due to time constraints, I figured it was safer to go with
> something simpler that I didn't have to learn as I go and could be
> done live without needed extra hardware on site. Plus it would be
> something that works at any site I needed it without extra software
> too.

Rear 'might' be quick and easy. It is intended to be almost
unattended and do everything for you. As for extra software - it is a
'yum install' from EPEL. The down side is that if it doesn't work,
it isn't very well documented to help figure out how to fix it. I'd
still recommend looking at it as a backup/restore solution with an
option to clone. With a minimum amount of fiddling you can get it to
generate a boot iso image that will re-create the source filesystem
layout and bring up the network. Then, if you didn't want to let it
handle the backup/restore part you could manually rsync to it from the
live system.

--
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Old 07-11-2012, 04:59 AM
Emmanuel Noobadmin
 
Default Best way to duplicate a live Centos 5 server?

On 7/11/12, Les Mikesell <lesmikesell@gmail.com> wrote:
> Hours? This should happen in the time it takes to transfer a
> directory listing and read through it unless you used --ignore-times
> in the arguments. If you have many millions of files or not enough
> RAM to hold the list I suppose it could take hours.

Not that many files definitely, more in the range of tens of
thousands. But definitely more than an hour or two with small bursts
of network traffic.

> Rear 'might' be quick and easy. It is intended to be almost
> unattended and do everything for you. As for extra software - it is a
> 'yum install' from EPEL. The down side is that if it doesn't work,
> it isn't very well documented to help figure out how to fix it. I'd
> still recommend looking at it as a backup/restore solution with an
> option to clone. With a minimum amount of fiddling you can get it to
> generate a boot iso image that will re-create the source filesystem
> layout and bring up the network. Then, if you didn't want to let it
> handle the backup/restore part you could manually rsync to it from the
> live system.

I'll look into it when I need to do this again. It just isn't
something I expect to do with any regularity and unfortunately server
admin isn't what directly goes into my salary so it has to take a
second priority.
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Old 07-11-2012, 03:11 PM
Les Mikesell
 
Default Best way to duplicate a live Centos 5 server?

On Tue, Jul 10, 2012 at 11:59 PM, Emmanuel Noobadmin
<centos.admin@gmail.com> wrote:
> On 7/11/12, Les Mikesell <lesmikesell@gmail.com> wrote:
>> Hours? This should happen in the time it takes to transfer a
>> directory listing and read through it unless you used --ignore-times
>> in the arguments. If you have many millions of files or not enough
>> RAM to hold the list I suppose it could take hours.
>
> Not that many files definitely, more in the range of tens of
> thousands. But definitely more than an hour or two with small bursts
> of network traffic.

Perhaps you have some very large files with small changes then
(mailboxes, logfiles, db's, etc.). In that case the receiving rsync
spends a lot of time copying the previous version of the file in
addition to merging the changed bits.

>> Rear 'might' be quick and easy. It is intended to be almost
>> unattended and do everything for you. As for extra software - it is a
>> 'yum install' from EPEL. The down side is that if it doesn't work,
>> it isn't very well documented to help figure out how to fix it. I'd
>> still recommend looking at it as a backup/restore solution with an
>> option to clone. With a minimum amount of fiddling you can get it to
>> generate a boot iso image that will re-create the source filesystem
>> layout and bring up the network. Then, if you didn't want to let it
>> handle the backup/restore part you could manually rsync to it from the
>> live system.
>
> I'll look into it when I need to do this again. It just isn't
> something I expect to do with any regularity and unfortunately server
> admin isn't what directly goes into my salary so it has to take a
> second priority.

ReaR's (Relax and Restore) real purpose is to be a full-auto restore
to the existing hardware after replacing disks, etc., something that
is relatively hard to do with complex filesystem layouts (lvm, raid,
etc.) and something armchair sysadmins are likely to need when they
least expect it. It does that function pretty well with a couple of
lines of config setup (point to an NFS share to hold the backup) for
anything where live tar backups are likely to work. The whole point
of the tool is that you don't need to know what it is doing and pretty
much anyone could do the restore on bare metal. Using it to clone or
to move to a modified layout is sort of an afterthought at this point
but it is still not unreasonable - it is just a bunch of shell scripts
wrapping the native tools from the system but you have to figure out
the content of the files where it stores the layout to build.

--
Les Mikesell
lesmikesell@gmail.com
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